The present invention relates to compounds useful in the inhibition of the chemotactic activation induced by the fraction C5a of complement and from other chemotactic proteins (chemokines) that exert their action by activating a 7-transmembrane-domain (7-TM) receptor. Said compounds are quaternary ammonium salts of R-2-arylpropionamides useful in the treatment of pathologies depending on the chemotactic activation of neutrophils and monocytes induced by the fraction C5a of the complement. In particular, the compounds of the invention are useful in the treatment of psoriasis, rheumatoid arthritis, ulcerative colitis, acute respiratory distress syndrome, idiopathic fibrosis, glomerulonephritis and in the prevention of injury caused by ischemia and reperfusion.